S-69-01

A brain bank for the identification of genes affecting brain structure

E. Meisenzahl. Psychiatrische Klinik tier Ludw, Miinchen, Germany

S-69-02

Genes which infuence the structure of the normal brain

I. Giegling, D. Rujescu, A. Kirner, T. Frodl, G. Schmitt, S. Ufer, G. Leinsinger, U. Hegerl, K. Hahn, H.-J. MNler, E. Meisenzahl. University of Munich Dept. of Psychiatry, Munich, Germany

Despite the considerable interindividual variation in the size of the human brain, the etiology of less extreme differences is largely unknown. Twin studies point towards a substantial heritability of differences in brain size, and more detailed analyses indicates that strong genetic influences contribute to the variability of each brain structure studied up to now. Recently it was shown that the estimated heritability is 81% for intracranial volume, 79% for the midline cross-sectional area of the corpus callosum, and 79% for lateral ventricle size. Interestingly, the manner in which the brain responds to the environment with advancing age is also genetically determined to a large degree, as demonstrated for the enlargement of the lateral ventricles. Despite the major genetic contribution to the variability of brain morphology there is, as yet, only few data available on candidate chromosomal regions or genetic variations which might contribute to these individual variations in humans. Brain development depends on a complex and tightly regulated sequence of events which are highly organized in terms of time and space. Genetic variations that affect the ability of neural ceils to proceed through these precisely defined steps ofneurodevelopment may cause developmental delays, which are often accompanied by early death of the affected neurons. Thus, genes which are known to participate in neurodevelopment and/or neurodegeneration seem to be appropriate candidate genes. We will report on first common genetic polymorphisms which may influence individual differences of brain volume in healthy volunteers. These, however, being novel findings should warrant further investigation. Nevertheless, our results will hopefully stimulate further studies in this emerging field.

S-69-03

The brain structural phenotypes of schizophrenia and bipolar disorder

C. McDonald. Institute of Psychiatry Psychological Medicine, London, United Kingdom